Various physiological, pharmacological, and biochemical data gathered over the past twenty-five years have led investigators to suggest a relationship of catecholamines to human hypertension. The Catecholamine Laboratory of the Mount Sinai School of Medicine has developed biochemical techniques by which human catecholamine metabolism can be evaluated with considerable specificity and sensitivity. Application of the procedures has led to the observation that defective catecholamine metabolism is not only associated to a gross degree with tumors of the neural crest but, in a much more subtle manner, with essential hypertension as well. This project is designed to investigate in greater depth, the original obsevations and their detailed causes, the effects upon catecholamine metabolism caused by drugs known to be of value in the treatment of essential hypertension, and an evaluation of the degree of reliability of certain catecholamine mesurements in the differential diagnosis of the manifold types of subjects with hypertension in order to further delineate the nature of this defect in norepinephrine metabolism. In vitro paradigms derived from human tissue of normal and hypertensive subjects will also be used in order to develop insight into the role of the catecholamines in the hypertensive diathesis.